Due to recent technology developments, processors, memory cards, and other components in electronic devices, e.g., computers, have increased in working frequency and power consumption. As a result, the amount of heat produced by these components as a side effect of normal operation may have also increased. To prevent possible overheating of such components, which may lead to malfunction and damage of the electronic devices, temperatures of those components usually need to be monitored, and kept within a reasonable range by dissipation of heat generated by those components, i.e., the components to be cooled. Dissipation of heat generated by those components may also improve their reliability.
Heat dissipation techniques for electronic devices may include using heat sinks and fans for air cooling. For example, heat sinks may be used to transfer thermal energy from the component(s) to be cooled to the surrounding cooler air. A heat sink may comprise a metal structure with flat surfaces to ensure good thermal contact with the component(s) to be cooled. However, heat sinks may be insufficient for some electronic devices.
As an alternative, a fan may be introduced into the electronic device to generate airflow around the component(s) to be cooled. A faster speed of the fan may lead to better cooling efficiency, because the fan may move heated air away from the component(s) to be cooled and draw cooler air over them more quickly. The fan may also be used in combination with heat sinks to further improve cooling efficiency. There are different types of fans and ways of controlling them. For example, 3-wire direct current (DC) fans and 4-wire pulse-width modulation (PWM) fans are among popular fans that may be used to dissipate heat from components in electronic devices such as computers. A 4-wire PWM fan may or may not include an internal pull-up resistor. The 4-wire PWM fan with an internal pull-up resistor complies with the Intel® 4-wire PWM fan specification.
FIG. 1 illustrates an input/output interface 102 for a conventional 3-wire DC fan 104. The input/output interface 102 has a ground terminal 106, a voltage control terminal 108, and a tachometer terminal 110. The voltage control terminal 108 is an input terminal, and the tachometer terminal 110 is an output terminal providing a tachometer signal that has a frequency proportional to the operating speed of the 3-wire DC fan 104. The speed of the 3-wire DC fan 104 may be described by a parameter “revolutions per minute” (RPM). Therefore, the tachometer signal indicates the speed or RPM of the 3-wire DC fan 104 and may be used for closed-loop speed control of the 3-wire DC fan 104. By changing a voltage applied to the voltage control terminal 108 of the 3-wire DC fan 104, the speed of the 3-wire DC fan 104 may be controlled. For example, if the 3-wire DC fan 104 is adapted to have a maximum input voltage 12 V, the voltage applied to the voltage control terminal 108 may vary from 4 V to 12 V during fan operation. The operating speed of the 3-wire DC fan 104 would generally vary in a direct relationship to the magnitude of the voltage applied to the voltage control terminal 108.
FIG. 2 illustrates an input/output interface 202 for a conventional 4-wire PWM fan 204. The 4-wire PWM fan 204 can be either a 4-wire PWM fan with an internal pull-up resistor or a 4-wire PWM fan without an internal pull-up resistor. The 4-wire PWM fan 204 has a ground terminal 206, a power terminal 208, a tachometer terminal 210, and a PWM control terminal 212. The power terminal 208 and the PWM control terminal 212 are usually input terminals, and the tachometer terminal 210 is an output terminal providing a tachometer signal that has a frequency proportional to the operating speed of the 4-wire PWM fan 204. Therefore the tachometer signal indicates the speed or RPM of the 4-wire PWM fan 204 and may be used for closed-loop speed control of the 4-wire PWM fan 204.
The speed of the 4-wire PWM fan 204 may be controlled by changing a duty cycle value of a signal applied to the PWM control terminal 212, i.e., the PWM control signal. For example, a PWM control signal with a 50% duty cycle value may control the 4-wire PWM fan 204 to operate at a speed that is 50% of the fan's full speed. Similarly, a PWM control signal with an 80% duty cycle value may control the 4-wire PWM fan 204 to operate at a speed that is 80% of the fan's full speed. In other words, as the duty cycle value of the PWM control signal is increased or decreased, the operating speed of the 4-wire PWM fan 204 correspondingly increases or decreases.
Typically, an electronic device is designed to support one type of fan. As a result, a user of the electronic device may need to select a specific fan for the electronic device, which may cause inconvenience to a user that does not know the fan specification of the electronic device. For example, when a computer user needs to select a fan for the computer, the user may first need to check the motherboard of that computer to determine which type of fan the motherboard supports.